It is not unusual for two stars or planets to be aligned with the Earth. What can we observe then? Depending on their apparent size, the more distant object may disappear, and therefore be eclipsed, but it may also be only partially occulted. On 12 August, there will be a solar eclipse... so we need to be prepared. This will be the subject of the conference, but we'll also be talking about other alignments that are just as remarkable and even extremely useful.